what do you call the block that moved up relative to the other?

In geology, the block that moved up relative to the other along a fault is usually called the upthrown block (or upthrown side of the fault).

More specific terms depend on the fault type:

• In a reverse or thrust fault , the hanging wall is the block that has moved up relative to the footwall.

• In a fault-block mountain setting, an uplifted block between two normal faults is called a horst , while the down-dropped block is a graben.

So if you just want the general name in a fault context, “upthrown block” (or “upthrown side of the fault”) is the standard term.